Prick punch



Aug. 30, 1932. J CQX 1,874,460

PRICK PUNCH Filed June 27, 1930 a 14W [ii] r 1 Q :5 30 IIIIIl/IA 5.9 55 3o 7 & INVENTOR 51 5 (c Ja zfaz.

Patented Aug. 30, 1932 PATENT OFFICE JOHN E. P. COX, OF ROCHESTER, NEW YORK Enron rnnon Applicationfiled June 27,

My present invention relates to machine tools and more particularly to prick punches, and it has for its, object to provide a simple, light and convenient punch of this character 5 particularly adapted for marking sheet metal plates and so devised that, though the plate or work piece obscures the'punch point, itself, the operator may nevertheless accurately position the spot upon which the blow to is delivered and position it in all directions without the use of a gauge.

To these and other ends, the invention resides in certainimprovements and combinationsof parts, all of which will be herein- .15 after described, the novel features being pointed out in the claims at the end of the specification.

In the drawing:

Fig. 1, is a side elevation of a portable 2 prick punch constructed in accordance with and illustrating one embodiment of my invention;

Fig. 2 is an enlarged fragmentary vertical section through-the anvil element; 7 I Fig. 3 is an enlarged fragmentary central section through that portion of the frame containing the punchingelement, the same beingshown in proper cooperative relationship with the anvil of Fig. 2;

Fig. 4 is a further fragmented section in duplication of a portion of the showing of Fig. 3 but with the actuating element in a different position", and

Fig. 5 is a cross section taken on the line 55 of Fig. 3. I

Similar reference numerals throughout the several views indicate the same parts.

The apparatus that I have illustrated in the drawing constitutes a portable prick punch as above indicated, which is taken to the work, instead of the work being taken to it, as a stationary fixture, although the invention may be used either way. Referring more particularly to the drawing; a rectangular frame is provided, as shown, the

top normally horizontal element of which is indicated at 1. This element 1 is tubular and carries at its front end an anvil element 2 having a hardened point. The anvil element embodies a stem 3 adapted for reciprocating upper end of which, is closed by a bushing or 1930. Serial N0. 464,215.

movement in a transverse bore in the tube 1.

A spring 4 surrounding the stem between the point 2 and the outside of the tube holds the anvil normally projected, as in Figs. 1 and 2, an outside head 5 on the upper end of the stem limiting this normal projected position. In other words, it is a yielding anvil and the purpose of its yieldability is to permit the machine to be used on work pieces of different thicknesses as the cooperatingv punch hereinafter described operates most effectively when its striking movement is of a uniformly maximum amplitude, as hereinafter described.

The rear end of the top frame tube 1 re- 05 ceives telescopically one arm of an L-shaped corner connection 6, the other arm of which telescopes within one arm of another tubular corner connection 7, all of the telescopically connected arms being relatively .adjustable and held relatively fixed in each instance in adjusted position by set grooves 8 and 9. The upright arms of the tubular corner piece 7 constitutes the rear rail of the frame while the other arm telescopes within a tubular lower rail 10 of the frame, being held similarly to corner connection 6 by a set screw 11. vRising from the front end of tubular lower rail 10 and fixed thereto or preferably integral therewith, as shown, is a tubular casing 12 containing the punchmechanism hereinafter described, including the prick punch point 13 in alinement with the anvil point 2. It will be seen from the foregoing without further description that by loosening the set screws 8, 9 and 11, the frame of the machine may be extended both vertically and horizontally in its proportion to accommodate work pieces of a wide range of sizes, both as to thickness and surface area, without disturbing the alinement of the punch and anvil elements 13 and "2 and enabling the latter to be positioned at any desired point farin from the edge of a Work piece, such as .an extensive plate of sheet metal.

. The punch mechanism shown is constructed asfollows: threaded within the otherwise open upper end of thetubular casing or support 12 at 14 is an inner tubular casing 15, the

threaded bearing plug 16; the prick punch point 13 in its normal retracted position rests upon the plug 16, where it is held by a light spring 17 surrounding its stem 18 and acting against a cross pin 19 thereon and reacting against the head of the plug; lower down the stem rests against a hammer 20 shaped to constitute a guiding surface against the walls of the tubular casing 15 a strong spring 21 is interposed between the hammer 20 and the bottom of casing 15 while projecting downwardly through said spring and through the bottom of casing 15 is an extension of the hammer that terminates below'said casing in a conical cam-faced, or pointed detent 22,

presenting a square shoulder at its upper portion. I I r The operation of this punch mechanism is obvious. I When the hammer 20 is drawn down against the tension of spring 21 and then released, the energy of the said compressed spring returns it sharply with an impact against the stem 18 that drives the punch point 13 upwardly toward the anvil'point 2 while overcoming the slight resistance of the small retracting spring 17 and punch-marks the underside of the work piece.

- The advantage here gained is that what I have termed the anvil 2 acts very slightly as such except onvery thin and light work, its mfl'or purpose being to designate the point at which the punch is made, even though the punch point is completely concealed by the work plece. In other words, itis an indicatoror guide for bringing the'punch point to the desired spot on the work with reference to the extent of the latter in allidirections.

"The actuating mechanism that retracts and releases the hammer 2-0 in the manner described embodies a cylindrical weight 23 slidable vertically as aguide in the tube 12an.d carrying a vertically disposed spring arm 24. At the upper end of the spring arm is a pawl or hook 25, below which is formed a cam 26. The spring arm is normally in the position of Fig. 3, in which its tension holds it in a proper position against a stop pin 27 The lower end of the guide weight 23 is pivotally connected at 28 and29 by a link 30 with one arm 31 of an operating lever 32 fulcrumed at 33 between bearin ears 34 (Fig. 5) on lower frame piece 10. T e spring 35 interposed between the latter and the operating lever arm 32 counterbalances the weight 23 to normally retain the parts in the position of Fig. 3.

In the operation of the machine, after the punch has been positioned on the work, as heretofore described, the operating arm 32 is first depressed causing the pawl 25 to rise and hook over the detent 22 of the hammer, which detent, because of its shape, forces the pawl to yield and then snap into place. The operating lever 32 is then raised sharply, which draws down the hammer 20 and energizes the spring 21 until the cam 26'on the pawlengages pin 27, as shown in Fig. 4, at which time the pawl on its spring arm 24 is deflected, instantaneously releasing the hammer and causing it to exert its impact against the lower end of the stem 18 of the punch 13. The actuating and operating parts then return to the normal positions indicated in Fig. 3 for the reasons stated during the descriptions thereof.

I claim as my invention:

1. In a prickpunching machine, the combination with a frame embodying a guide, a hammer adapted to reciprocate in the guide, a

prick punch also supported in the guide to receive impact from the hammer, the latter being provided with a cam-faced detent, a spring for driving the hammer, and actuating meansfor the latter embodying a pawl movable in one direction to engage the detent and in the other direction to retract the hammer and energize the spring, and means for tripping the pawl and releasing the detent at a predetermined point.

2. In a prick punching machine, the combination with a frame embodying a guide, a hammer adapted to reciprocate in the guide, a prick punch also supported in the guide to receive impact from the hammer, the latter being provided with a cam-faced detent, a spring for driving the hammer and actuating means for the latter embodying a spring pawl movable in one direction to engage the detent and in the other direction to. retract the hammer and energize the spring, said spring pawl being provided with a cam, and an abut ment cooperating with the cam on the pawl when moved a predetermined distance in said opposite direction for abruptly releasing the retracting means.

3. In a prick punching machine, the combination with a frame embodying a tubular guide havin a bearing in the end thereof and a prick punc reciprocatable in the bearing, a tubular casing within the tubular guide, a hammer reciprocatable in the tubular casing to cooperate with the prick punch, a spring within the casing for driving the hammer, the latter being provided with a detent, a weight reciprocatable in the tubular guide and carrying a spring pawl provided with a cam, said pawl being adapted to engage the detent when the weight is moved in one direction and to retract the hammer and energize the sprin when moved in the opposite direction, an a utment in the path of the cam for retracting the pawl at a predetermined point and releasing the spring and hammer,

an operatin lever for moving the weight in both directions, and a spring tending to counterbalance the wei ht.

J HN E'. P. GOX. 

